Due to its unique characteristics, barium carbonate is considered a versatile chemical for use as an additive for enhancing the physical properties of glass, ceramic ware, permanent magnet and the like, and for reacting with titanium dioxide to manufacture barium titanate of ceramics having a strong dielectric characteristic.
Conventionally, barium carbonate is produced by first reducing a barium sulfate by coke at an elevated temperature (1150.degree.-1200.degree. C.) to form a soluble barium sulfide, which is then reacted with alkali metal carbonate or bicarbonate to form a barium carbonate. The reaction scheme of the above process is as follows: EQU BaSO.sub.4(s) +4C.sub.(s) .fwdarw.BaS.sub.(s) +4CO.sub.(g) ( 1) EQU BaS.sub.(aq) +M.sub.2 CO.sub.3(aq) .fwdarw.BaCO.sub.3(s) +M.sub.2 S.sub.(aq) ( 2)
wherein the M is Ma or K.
In the above reactions, the quality of the resulting barium carbonate depends upon the purity and activity of coke. Generally, reducing potential of coke in the reaction is low because of the relatively low reducing activity of coke itself and the limited contact area of the granular form of coke, and therefore the purity and yield of the barium carbonate obtained by the above process are not satisfactory. In addition, the reaction must be carried out at an elevated temperature, therefore, more sophisticated heat resistant facilities and extra-fuel for heating up the reaction are needed.
In order to overcome the above mentioned disadvantages of the conventional method for producing barium carbonate, the inventor has studied extensively on this subject and found that barium carbonate of high purity can be produced with a high yield according to the following method: heating coal tar pitch to a specific temperature to form mesophase and adding barium sulfate to react with the mesophase, and then heating the reactants to a desired temperature after maintaining the temperature for a predetermined period of time, and finally, reacting the resulting mixture with alkali metal carbonate or bicarbonate to convert into barium carbonate. This invention provides such an improved method.
Therefore, the object of present invention is to provide a novel method for producing barium carbonate.